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Google Summer of Code with Boost
by David Bellot 28 Jan '18

28 Jan '18

Hi everyone, still a few days before we submit our proposal to Google. Don't loose the chance to become a mentor for Boost. It shines on your CV, it is a great opportunity to work with brilliant students around the world, it makes you an official C++ world-wide expert. So far, we have a nice but little list of proposals here: https://github.com/boostorg/boost/wiki/Boost-Google-Summer-of-Code-2018 It would be good to have a bit more before I go and submit to Google. This will increase our chances to be selected again this year. For Boost it's a great funding worth several thousand of dollars every year. We just don't want to miss it. Best regards, David

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[gsoc18] New Astronomy Library
by Pranam Lashkari 28 Jan '18

28 Jan '18

Boost has developed many libraries which is useful in the field of science. I would like to propose a library for "Astronomy" as a student. I have been an amateur astronomer since last 8 years and being a Computer Engineering student I will be able to develop this library with little mentoring. I have some ideas about what can be integrated into it, which I can propose if the proposal seems promising. If so are there anyone who can help me out with this and mentor me? Thank you, Pranam Lashkari

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[gsoc18] ublas project 3
by Aperjump 28 Jan '18

28 Jan '18

I'm Wei Wang, a CS master student focusing on high-performance computing field. `boost::ublas` project 3 adding GPU computation interests me a lot and I'd like to help add this feature to ublas. I find this project was also on last years' list and I'm curious if anyone did this before or on which stage he/she has finished. I've already read the initial source code of `ublas` in `boost 1.29`(I also read 1.66 API, and found it add one concept `container`, which used to be `bounded_array` and `unbounded_array`). I wrote a passage describing its template parameter deduction relationships. Besides, I wrote a series blogs teaching how to use openCL efficiently with proper data partition and memory usage. This is my first time participating in GSOC, and I'm a bit of confused on following question: 1. Integrating openCL requires preparing for context, command_queue, event and other "environment objects", should they also be included in this lib? 2. Take matrix matrix multiplication A*B for example. The last stage before matrix copy assignment is in `matrix_matrix_prob` class and its evaluation requires loop through all items on both matrix. If I want to add GPU compute features, I need to launch kernel for each computation expression at this step, but it seems to be contradictory to `ublas`'s lazy evaluation rationale. How to reconcile that? 3. What should I implement in the competency matrix class? Just integer matrix or template matrix class?Should I support current `ublas` interface(those typedefs and traits)? Best regards, Wei Wang -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Dev-f2600599.html

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Re: [boost] [review] outcome broken on clang/libstdc++ (Linux) and Apple clang/libc++ and gcc 7.2
by Glen Fernandes 28 Jan '18

28 Jan '18

I wrote a .travis.yml for your boost-outcome submission to run your unit tests against a few compilers: The output is at: https://travis-ci.org/glenfe/ned14.outcome/builds/334222400 I updated it to make sure the clang++-libstdc++ uses a more recent libstdc++. It looks like: - clang++-libc++ fails because of forgetting to #include a header. - GCC 7.2 with -std=c++17 is the one with the Internal Compiler Errors (I didn't investigate further) - clang++5-libstdc++ fails because it cannot find a type in std Is there a reason why you don't have travis and appveyor for boost-outcome? I remember your "Best Practices" document strongly advocating that every Boost library submission should have them. Glen

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Re: [boost] [review] outcome broken on clang/libstdc++ (Linux) and Apple clang/libc++ and gcc 7.2
by Glen Fernandes 27 Jan '18

27 Jan '18

On Sat, Jan 27, 2018 at 4:55 PM, Glen Fernandes wrote: > I just tried boost-outcome unit tests with clang 4.0, 5.0 on Linux > with libstdc++ with -std=c++14 and -std=c++1z which fails with many > errors: > > e.g. [snip] > In file included from > libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:34: > libs/outcome/test/tests/../../include/boost/outcome/detail/../success_failure.hpp:54:42: > error: no template named 'conditional_t' in namespace 'std'; did you > mean 'conditional'? > template <class T> using devoid = > std::conditional_t<std::is_void<T>::value, void_type, T>; > ~~~~~^~~~~~~~~~~~~ > conditional > /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:1780:12: > note: 'conditional' declared here > struct conditional > ^ > > > Then I also tried the boost-outcome unit tests with Apple clang 8.1.0 > with libc++ with -std=c++14 and -std=c++1z which fails with errors > like: > I pasted the wrong error output here; the right error output is: clang-darwin.compile.c++ bin.v2/libs/outcome/test/core-outcome.test/clang-darwin-4.2.1/debug/cxxstd-14-iso/tests/core-outcome.o In file included from libs/outcome/test/tests/core-outcome.cpp:30: In file included from libs/outcome/test/tests/../../include/boost/outcome/outcome.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/outcome_exception_observers.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:35: libs/outcome/test/tests/../../include/boost/outcome/detail/value_storage.hpp:181:22: error: no matching constructor for initialization of 'value_type' (aka 'boost::outcome_v2::outcome<int, std::__1::error_code, std::exception_ptr, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::__1::error_code, std::exception_ptr> >') new(&_value) value_type; // NOLINT ^ libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:270:11: note: in instantiation of member function 'boost::outcome_v2::detail::value_storage_nontrivial<boost::outcome_v2::outcome<int, std::__1::error_code, std::exception_ptr, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::__1::error_code, std::exception_ptr> > >::value_storage_nontrivial' requested here : _state(std::move(o._state)) ^ > Is this also a known issue? Only gcc 6 and gcc 7 with lisbtdc++ on > Linux seem to pass. The other combinations I tried (clang + lisbtdc++ > on Linux, Apple clang + libc++) do not. > I spoke too soon, here gcc 7 does not pass. It ICEs: libs/outcome/test/tests/../../include/boost/outcome/detail/result_value_observers.hpp:45:17: in constexpr expansion of ‘((boost::outcome_v2::detail::result_value_observers<boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >, int, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >*)this)->boost::outcome_v2::detail::result_value_observers<boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >, int, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >::<anonymous>.boost::outcome_v2::detail::result_storage<int, std::errc, boost::outcome_v2::policy::error_code_throw_as_system_error<int, std::errc, void> >::result_storage<int>(boost::outcome_v2::in_place_type_t<int>(), <anonymous>)’ libs/outcome/test/tests/core-result.cpp:330:41: internal compiler error: in adjust_temp_type, at cp/constexpr.c:1206 constexpr result<int, std::errc> a(5), b(std::errc::invalid_argument); [...] 0x6db788 cxx_eval_constant_expression ../../src/gcc/cp/constexpr.c:4034 Please submit a full bug report, with preprocessed source if appropriate. Please include the complete backtrace with any bug report. See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions. Let me know if you need more context, but it appears boost-outcome is also broken on gcc 7.2. Glen

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Re: [boost] [review] outcome broken on clang with libstdc++ (Linux) and Apple clang with libc++
by Glen Fernandes 27 Jan '18

27 Jan '18

On Sat, Jan 27, 2018 at 3:07 PM, Niall Douglas wrote: > b2 libs/afio/test works fine with VS2017. So it would seem that that ICE > Vinnie encountered is some weird corner case nobody could have > anticipated. As I mentioned, almost all of the development of Outcome > was done on MSVC. It's very well tested on MSVC, and I've never seen > anything like that ICE before. I just tried boost-outcome unit tests with clang 4.0, 5.0 on Linux with libstdc++ with -std=c++14 and -std=c++1z which fails with many errors: e.g. In file included from libs/outcome/test/tests/comparison.cpp:35: In file included from libs/outcome/test/tests/../../include/boost/outcome/outcome.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/outcome_exception_observers.hpp:34: In file included from libs/outcome/test/tests/../../include/boost/outcome/detail/result_storage.hpp:34: libs/outcome/test/tests/../../include/boost/outcome/detail/../success_failure.hpp:54:42: error: no template named 'conditional_t' in namespace 'std'; did you mean 'conditional'? template <class T> using devoid = std::conditional_t<std::is_void<T>::value, void_type, T>; ~~~~~^~~~~~~~~~~~~ conditional /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:1780:12: note: 'conditional' declared here struct conditional ^ Then I also tried the boost-outcome unit tests with Apple clang 8.1.0 with libc++ with -std=c++14 and -std=c++1z which fails with errors like: clang-darwin.compile.c++ bin.v2/libs/outcome/test/outcome-int-int-1.test/clang-darwin-4.2.1/debug/cxxstd-14-iso/outcome-int-int-1.o libs/outcome/test/compile-fail/outcome-int-int-1.cpp:12:26: error: no matching constructor for initialization of 'outcome<int, int, int>' outcome<int, int, int> m(5); ^ ~ libs/outcome/test/compile-fail/../../include/boost/outcome/outcome.hpp:222:31: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'int' to 'const boost::outcome_v2::outcome<int, int, int, boost::outcome_v2::policy::all_narrow>' for 1st argument class BOOST_OUTCOME_NODISCARD outcome ^ Is this also a known issue? Only gcc 6 and gcc 7 with lisbtdc++ on Linux seem to pass. The other combinations I tried (clang + lisbtdc++ on Linux, Apple clang + libc++) do not. Glen

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Re: [boost] [review] outcome broken on MSVC, plus questions
by Glen Fernandes 27 Jan '18

27 Jan '18

Hi Niall, Still working on the review; I had the following questions while reading the threads: 1. Which versions of MSVC 2017 does boost-outcome not work on, right now? 2. According to the documentation, outcome and boost-outcome both require MSVC 2017, right? i.e. They do not support MSVC 2015 or lower? 3. Is standalone outcome fine with MSVC2017, only boost-outcome that is broken? 3.1. If so, is it right that the boost-outcome repository is "generated" from the outcome repository? And is that the reason that boost-outcome is broken on MSVC 2017? 4. Would you happen to know how does your outcome/result compare to Peter's outcome/result in variant2? (I saw you point out that Peter implemented expected, and then I saw he also had an outcome/result implementation in variant2). 4.1. What different compilers and standards does his support compared to yours? 4.2. What kind of code is generated from his implementation compared to yours? Thanks, Glen

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[outcome] Purpose of value_type_if_enabled?
by Bjorn Reese 27 Jan '18

27 Jan '18

Are value_type_if_enabled and error_type_if_enabled supposed to be used by the library users? If so, how?

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[spirit]why x3::alternative::parse not short-circuited?
by Larry Evans 27 Jan '18

27 Jan '18

https://github.com/boostorg/spirit/blob/develop/include/boost/spirit/home/x… shows both left.parse *and* right.parse are called. Shouldn't right.parse be skipped if left.parse succeeds?

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[outcome] Andrzej's review
by Andrzej Krzemienski 27 Jan '18

27 Jan '18

Hi Everyone, This is my review of Boost.Outcome v2. The library should be *accepted* subject to conditions that I list down below. What is your evaluation of the design? Clean and logically divided. What is your evaluation of the implementation? > Some bugs aside, it is clean and well structured. I was able to read it and understand how things work. I will be filing bugs in GitHub. What is your evaluation of the documentation? > Good. You can get the idea what the library is doing and how you can use it. But I should mention that I wrote some pieces thereof, so my opinion is likely biased. The docs need some modifications before they can get into Boost. I mean macro names, and the technology required to build it. What is your evaluation of the potential usefulness of the library? > I find the library very useful in certain domains. I myself have found two applications in my job project, and they are not really related to light-speed efficiency: 1. We have a task scheduling framework built atop ASIO, and signalling failures through exceptions makes the code really difficult to read because try-catch blocks need to work as control statements. Also, we cannot pass them by exception_ptr as sometimes we need to classify the kind of failure to determine if we want to deal with it in the framework, or if we want to forward them to the user. 2. I have a validation routine that validates (and parses) the input data written using some syntax. I wan the syntax-errors in input files to be forwarded as failed `result`s (no exceptional about these), but other errors like memory shortage during the file parsing to be signaled via exceptions (and I will probably kill the module in response). Why accepting this library when we have `expected` being standardized? I do not really mind having two in Boost. First, it is ready, being proposed, and applied in a number of non-trivial code-bases. Niall claims that his trade-offs are better tailored to predictable-latency applications. I do not have enough knowledge to asses it. They look convincing. The only way to test it is to give this library the Boost blessing and have the user test it. I am bought by the TRY operations, and the upgrade to `outcome` looks really convincing. Did you try to use the library? With what compiler? Did you have any > problems? > Yes. A lot of compilers. For instance GCC 6.4.0, also different GCC and Clang versions in WandBox. No problems encountered. How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > I have read most of the final implementation. I have read many versions of the documentation. I have spent a lot of time (prior to the review) asking Niall lots of questions about the details. I have also built lots of small examples to test the library and some corner cases. Are you knowledgeable about the problem domain? > I do report failures (by different means) in my programs. I have given it quite some thought. I am well familiar with implementation and formal specification of `boost::optional` and `std::optional` which had to address some similar implementation problems. Do you think the library should be accepted as a Boost library? > Yes, conditionally. Here are three conditions: 1. Documentation is adjusted to use boost-standard names of macros and namespaces. Also, it is not clear if Boost release process is capable of handling the technology that Niall has chosen. If not, the contents of documentation should be migrated to another format, manageable by Boost release process. 2. Because there has been some confusion around the meaning of storing default-constructed `std::error_code` (is it an error or lack thereof?) and `std::exception_ptr` (e.g., see this issue: https://github.com/ned14/outcome/issues/115) I request that you state in the docs, before the API Reference how library treats default-constructed values of `EC` and `EP`. For instance, you can say "default-constructed error_code is considered an error, and treated as such by the library", or "the library sometimes may make use of the fact that a default-constructed EC/EP is not an error, so make sure not to pass us such values": I am fine with any answer, but I need you to spell it out, so that I know what to expect. 3. Similarly, I request that you put in the docs what is the "value" of an object of type `outcome<>` or `result<>` in the sense in which John Lakos talks about "salient attributes". I know that T, EC, and EP constitute the value. But in the middle of the tutorial we learn that apart from these you also store "spare_storage" -- is it also included in copying and comparisons? API reference on `operator==` only says "compares if two objects are equal", but it is not that clear what it means. Also, what does it mean that result is equal to optional. Define it somewhere and paste links to it. Finally, I wan to thank Niall for his now many-year effort to deliver this really cool library to the community. Regards, &rzej;

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